EVALUATION
Use cached applet JNLP to start applet and perform update check in background if JNLP file specify background update check.
Root cause was we are using LaunchDesc.buildDescriptor(File f) when trying to load cached jnlp, but that only works for dragged out applets. We should use using LaunchDesc.buildDescriptor(File f, URL codebase, URL documentbase, URL originalRequest) when trying to load JNLP from cache instead.